Apparatus for packaging integrated circuit chips employing a polymer film overlay layer

ABSTRACT

A method and apparatus are provided for disposing a polymer film on an irregularly-shaped substrate at relatively high temperatures. In particular, the method and apparatus of the present invention provide a system for the packaging of very large scale integrated circuit chips. The system of the present invention particularly solves problems associated with high temperature processing and problems associated with the highly irregular surfaces that result. Nonetheless, the resultant product is capable of being fashioned into circuit chip systems which are independently testable and which may be reconfigured after testing by removal of the polymer film itself.

This is a division of application Ser. No. 240,367, filed Aug. 30, 1988,now U.S. Pat. No. 4,933,042, which in turn is a continuation ofapplication Ser. No. 912,455, filed Sept. 26, 1986, and now abandoned.

BACKGROUND OF THE INVENTION

The present invention is generally directed to a method and apparatusfor laminating a polymer film over the surface of an irregularsubstrate, particularly a substrate on which a plurality of integratedcircuit chips are affixed. More particularly, the present inventionrelates to a packaging method for electronic integrated circuit chips,particularly very large scale integrated (VLSI) devices. Moreover, themethod and apparatus of the present invention provides a polymer filmoverlay for not only retaining "microchips" on a substrate, but alsoprovides a means for interconnecting these devices. Even moreimportantly, the method and apparatus of the present invention provideremovable interconnection capabilities.

In the packaging of very large scale integrated circuit devices, a greatdeal of space is taken up by mechanisms for interconnecting one chip toan adjacent device. This makes the packaging of integrated circuitdevices and electronic components based thereon larger than necessary.As a result of this, many individuals are involved in the development ofso-called wafer-scale integration processes. However, the effortsexpended in these directions have generally tended to be limited by theproblem of yield. Because a certain number of chips or dies on a waferare often found to be defective, the number of wafers that are producedthat are completely usable is generally lower than is desired.Furthermore, there still exists the problem of interconnecting thevarious chips on a wafer and the concomitant problem of testing a largesystem, such as results when a number of highly complicated individualintegrated circuit components are interconnected. Accordingly, it isseen that it would be very desirable to be able to construct wafer scaleintegrated circuit packages from individual, easily testable integratedcircuit chips. It is to this end that the present invention is directed.

More particularly, the present invention is directed to a method andapparatus for applying a polymer film overlay. This film covers aplurality of integrated circuit chips disposed adjacent to one anotheron an underlying substrate. Furthermore, the polymer film of the presentinvention provides an insulative layer for interconnection of theseindividual circuit chips. A significant advantage of the system of thepresent invention is the ability to remove one or more of theseinterconnection layers so as to provide a multitude of arrangement andtesting capabilities.

One of the generic problems sought to be solved by the system of thepresent invention is the laminating of a polymer film to an irregularsubstrate. Certain laminating methods suffer from several deficienciesthat become extremely important when one is trying to dispose filmmaterial on integrated circuit devices. This is particularly true inthose circumstances in which passivation layers have not yet beenapplied to such devices. One method of continuous lamination isso-called roll lamination in which a substrate to be laminated is passedbetween two heated rollers and the pinching effect of the rollers,combined with heat, laminates the film to the substrate. Severalproblems exist in this approach. The approach is adequate if thesubstrate is perfectly flat. However, the rollers cannot comply to anirregular surface, with the result being a poor lamination in low spotsand overpressure effects in high spots. Also, a substrate with anirregular surface on the bottom side would damage the lower roller orthe substrate For example, pins coming down from the bottom of a packagewould be damaged. Another problem with roll lamination occurs when hightemperatures are required to process high temperature adhesives.Compliant materials are not available with high temperaturecapabilities. Silicone materials seem to be the best known compliantsubstances for this purpose. However, this material tends to revert to asticky goo at temperatures around 200° C. A third problem also existswith this methodology since it is necessary that the top roller touchthe material to be laminated. It is impossible then to preventcontamination on the top roller from contaminating the surface of thepolymer being laminated. This problem is especially serious with rollerscomprising silicone material. Silicone materials produce outgassingproducts which contaminate the top surface and prevent good adhesionwhen subsequent layers are applied to the top surface of the film beinglaminated.

A second method used in laminating involves the use of a vacuum bag. Inthis system, a bag formed of high temperature material is placed aroundthe materials to be laminated. The bag is evacuated and the bag placedin an oven. There are several problems associated with the vacuum bagmethodology, however. One problem is that it is not a continuousprocess. That is, material to be laminated must be placed in the bag,the bag evacuated, the bag placed in an oven for a period of time, andafter lamination, the laminated piece is removed from the bag. Automaticfeed of material is therefore precluded. The second problem with vacuumbag methodologies is that the pressure is limited to the outside airpressure, even in the face of a perfect vacuum. Still another problemwith this method is that the vacuum bag touches the top of the materialbeing laminated. Contamination from the bag can then be transferred tothe material being laminated.

A third laminating method is the standard press lamination. In thismethod, the material to be laminated is placed between two heatedplatens which are forced together by means such as a hydraulic jack.This technique works if the materials to be laminated are flat. If thesubstrate to be laminated is irregular in shape, or if there are smallparticles on the surface of the substrate to be laminated, very highpressures where the particles are present will punch through the film tobe laminated and no pressure is available at the low points on thesubstrate. The thinner the film, the greater this problem becomes. Apartial solution to this problem is the use of compliant pads to absorbsome of the pressure differential. However, compliant pads contaminatethe top surface of the film to be laminated and, in high temperaturesituations, there are no suitable compliant pad materials available. Anadditional problem of press laminating is that it takes time and energyto cool and heat the relatively high thermal mass platens. The platensmust be physically thick structures because they are required to takehigh pressures over a large area without bending. An additional problemwith press laminating is the removal of air and by products of theheating of adhesives during the lamination process, since the pressuretends to trap air and byproducts and tends to form blisters.

Additional problems occur when the film to be laminated to a substrateis a thermoplastic. Unless the top press pad has a special releaseproperty, the thermoplastic often will stick as well to the top presspad as it does to the substrate. Another problem exists in that nocompliant pad can provide the dual function of maintaining constantpressure on the thermoplastic film at the same time that it perfectlymatches the contour of the underlying substrate. Accordingly, it is seenthat certain laminating methodologies are inappropriate for use infacilitating the construction of wafer scale integrated circuit devices,as contemplated herein.

SUMMARY OF THE INVENTION

In accordance with a preferred embodiment of the present invention, amethod for applying a polymer film to an irregular substrate includesthe following steps. The film is disposed over the substrate in closeproximity to it, but not in substantial contact with it. Vacuumconditions are then applied above and below the film so as to maintainthe non-contact condition. The film is then heated under vacuumconditions and fluid pressure is applied above the film so as to move itinto contact with the substrate. As contemplated herein, the substrateis typically irregular because it has itself disposed thereon aplurality of integrated circuit chip dies. These dies may even representintegrated circuit chips from different chip technologies such assilicon based chips and gallium arsenide based chips. Such chips are notlimited to comprising only silicon based chips. As used herein and inthe appended claims "substantial contact" is that contact which wouldpreclude the removal of air and/or gaseous products.

In accordance with another preferred embodiment of the presentinvention, an apparatus for applying a polymer film to an irregularsubstrate comprises a substantially flat substrate holder assembly forsupporting the substrate and the polymer film at a certain distance overthe substrate. The apparatus is provided with a movable upper chamberwhich is sealable against the holder assembly and the film. A film riseris disposed on one side of the holder assembly so as to form a dam-likea structure around the substrate and disposed so as to be enclosable bythe movable chamber. Means are supplied to apply vacuum conditions to avolume bounded by the holder assembly, the film riser and the polymerfilm. Means are also provided to heat the film. The movable chamber isalso generally provided with means for applying both vacuum and pressureconditions on the upper surface of the film. As used herein and in theappended claims, the term "chamber" does not refer to a void, but ratherto means for defining an enclosed volume.

Accordingly, an object of the present invention is to provide a methodfor laminating a polymer film to an irregular substrate which providesfor removal of process gasses or trapped air at the surface of thepolymer film and the substrate and also provides for adding additionalpressure to the top surface of the film to be laminated.

Another object of the present invention is to provide a laminatingdevice which can accommodate to a continuous roll-to-roll process.

A further object of the present invention is to provide a device forlaminating a polymer film without contact to the top surface of the filmbeing laminated.

Yet another object of the present invention is to allow heating of thesubstrate from the bottom as well as heating from the top and to allowthe application of ultraviolet radiation for the purpose of curingphotosensitive material through a polymer layer.

A still further object of the present invention is to provide a methodof laminating thermoplastic layers which accurately follow the contoursof an irregular substrate and which do not need a release layer coveringa thermoplastic film.

Another object of the invention is to provide a device without highthermal mass platens so that heating can be accomplished by infraredenergy impinging directly on the surface and where fast cooling can beachieved by allowing a flow of gas or other coolant fluid over the topsurface of the film being laminated while still maintaining pressure onthe film.

Yet another object of the present invention is to provide a device forlaminating polymer films to an irregular substrate in which vacuum canfirst be applied until a melting or other predetermined temperature isreached, with subsequent application of pressure, thus allowing themaximum removal of gas before pressure forces final compliance of thefilm to be laminated.

A still further object of the present invention is to provide a devicein which special processing gasses can be admitted either between thesubstrate and the laminating film or above the laminating film.

Lastly, but not limited hereto, it is an object of the present inventionto provide a method for packaging integrated circuit devices and inparticular, packaging of such devices in a fashion so as to provideinterconnection means for wafer scale integration methodologies.

DESCRIPTION OF THE FIGURES

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the concluding portion of thespecification. The invention, however, both as to organization andmethod of practice, together with further objects and advantagesthereof, may best be understood by reference to the followingdescription taken in connection with the accompanying drawings in which:

FIG. 1 is a partial cross™sectional side elevation view of an apparatusin accordance with the present invention;

FIG. 2A is a cross-sectional side elevation schematic view showingdetail from a portion of FIG. 1 and more particularly illustrating therelationship of the polymer film and the substrate to be laminated priorto contact;

FIG. 2B is a view similar to FIG. 2A except that the film is now shownin contact with and complying to the surface of the substrate;

FIG. 3A is a view more particularly illustrating the use of separatelamination films and sealing films;

FIG. 3B is a cross-sectional side elevation view showing a detailed viewof the layered structures in FIG. 3A;

FIG. 3C is a view similar to FIG. 3A, but more particularly showing theutilization of a thermoplastic laminating film and a release sealinglayer;

FIG. 3D is a cross-sectional side elevation view showing a detailedportion of the layer structure in FIG. 3C;

FIG. 3E is a view similar to FIG. 3A, but more particularly showing theutilization of a thermoplastic laminating film with a thin metal depositthereon for release;

FIG. 3F is a cross-sectional side elevation view showing a detailedportion of the layered structure in FIG. 3E;

FIG. 3G is a view similar to FIG. 3A more particularly illustrating amethod for laminating a dry film resist;

FIG. 3H is a cross-sectional side elevation view more showing a detailedportion of the layered structure of FIG. 3G;

FIG. 4A is a view illustrating the use of a metal foil as releasemechanism, particularly for use with thermoplastic films;

FIG. 4B is a view similar to FIG. 4A, but more particularly including anaperture in the metal foil for facilitating the heating of substrate 33;

FIG. 5 is a cross-sectional side elevation view particularlyillustrating the utilization of cooling means to prevent thermoplasticmelting except over the substrate;

FIG. 6 is a partial cross-sectional side elevation view similar to FIG.1 more particularly illustrating an apparatus with continuousroll-to-roll capability.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a cross-sectional diagram illustrating the basic componentsof an apparatus 10 in accordance with a preferred embodiment of thepresent invention. The components of the apparatus include substrateholder 30 upon which workpiece 33 is positioned for processing.Substrate holder assembly 30 preferably includes infrared transmissivewindow 32 disposed in a recess in a holder assembly. Window 32preferably comprises a low thermal mass. Substrate holder assembly 30also includes fluid ports 31 for producing vacuum conditions beneathfilm (or seal material) 35. Also, substrate holder assembly 30 includesfilm riser 34 disposed on the holder assembly so as to support film 35above workpiece 33 so that contact between the film and the workpiecedoes not occur until desired.

The apparatus of FIG. 1 also includes upper, movable chamber 20 which issealable against holder assembly 30 and the polymer film by means ofgasket or seal 28. Upper chamber assembly 20 includes means forproducing both vacuum and pressure conditions above the polymer film. Inparticular, upper chamber 20 includes flow conduit 22 connected tothree-way valve 27 which is selectable to connect upper chamber 20 to avacuum pump through conduit 29a or to ambient atmospheric pressureconditions through conduit 29b. Upper chamber 20 also includes flowconduit 23 connected to pressure regulator 19 through valve 26. Thisprovides a means for applying fluid pressure above polymer film 35 whenmovable chamber 20 is positioned so as to be sealed against polymer film35 and substrate holder assembly 30 (as shown). Upper chamber 20 alsopreferably includes infrared transmissive window 21 disposed so as to besealably affixed as shown, using gasket or seal 25 and retentionassembly 24. Also preferably included is radiant infrared energy heatsource 18 which is disposed above window 21 and provided to heat film 35and workpiece 33 from above.

In a similar manner a lower chamber 40 is provided beneath window 32 andis structured so as to be sealably affixed to holder assembly 30, as forexample, by seals or gaskets 48. Lower chamber 40 is designed tomaintain either ambient atmospheric pressure or vacuum conditions. Lowerchamber 40 also preferably includes heater 41 together with infraredreflector 42 which is positioned so as to direct radiant infrared energythrough infrared transmissive window 32 so as to heat workpiece 33 andfilm 35 from below. Heater 41 is preferably electrically powered, as forexample, from feedthroughs 43. Lower chamber 40 also includes flowconduit 47 which is connected to three-way valve 44. This valve isselectable so as to connect the volume of lower chamber 40 with vacuumconditions through conduit 46, or to ambient air conditions as throughconduit 45.

Apparatus 10 shown in FIG. 1 is generally operable in the followingmanner to produce the result desired. In operation, a workpiece 33 isplaced on substrate holder assembly 30 and the workpiece is covered (butnot contacted) by the polymer film to be laminated. In one exemplaryembodiment, the workpiece is precoated with a thermoplastic adhesive.Upper chamber 20 is then forced into intimate contact with polymer film35 and substrate holder assembly 30. This forms a seal on one sidebetween the polymer film and the upper pressure chamber assembly, and onthe other side between the polymer film and the substrate holderassembly. Particular attention is now directed to vacuum ports 31 insubstrate holder assembly 30. When vacuum is drawn through these ports,through lower chamber 40, a vacuum is formed throughout the volume underthe polymer film up to the point where the polymer film seals with thesubstrate holder assembly. This vacuum removes air from between thepolymer film and the workpiece and allows intimate contact therewith.Generally, however, vacuum conditions may also be applied simultaneouslyto the upper chamber assembly 20 to keep the film from sealing irregularareas on the substrate which would prevent the lower vacuum fromremoving all gas from between the polymer film and the workpiece. Filmrisers 34 are important during this phase to keep the film from touchingthe workpiece. This is especially important when adhesive on theworkpiece becomes tacky. On subsequent heating, the vacuum removesoutgassing products generated by the heating of any adhesive, thepolymer film, and the workpiece. After suitable outgassing, pressure isapplied to the top of the polymer film by admitting gas or other fluidto the upper chamber assembly. A uniform pressure is now applied to thepolymer film throughout the volume of the upper chamber assembly out tothe point where the chamber assembly seals to the polymer film. The gasadmitted to the pressure chamber assembly cannot escape because of theseal between the pressure chamber and the polymer film. Heating of thesubstrate may be achieved in several different ways. In the preferredembodiment, the workpiece is placed on transparent window 32. Thisallows infrared radiation from lower heater element 41 to impingedirectly on workpiece 33 and to thereby heat the workpiece with verylittle heating of the window assembly. In addition, a window ispreferably placed in the upper pressure assembly and additionalradiative energy is applied to the polymer film from above and, throughthe polymer film, to the workpiece itself. Very rapid heating of thesubstrate is achieved because of the low thermal mass of the supportingstructure. Note also that hot gas or even a hot liquid can be admittedthrough inlet 23 of the pressure chamber to provide for very rapidheating on the surface of the polymer film. In addition, cooling can beeffected by supplying a cooling gas and providing a flow through anoutlet port of the upper chamber assembly such that pressure ismaintained on the polymer film while a flow of cooling gas rapidly coolsthe film and the substrate.

In accordance with a preferred embodiment of the present invention, themethod and apparatus disclosed herein is particularly adapted to thesituation in which workpiece 33 includes a substrate on which there isdisposed a plurality of integrated circuit chips. These chips may beaffixed to the substrate by any suitable adhesive means. Accordingly, inaccordance with the present invention, the resultant product comprises asubstrate containing a plurality of integrated circuit chips covered bya thin polymer film in which apertures may be formed and on whichconductive patterns may be disposed so as to interconnect the integratedcircuit chips. In accordance with preferred embodiments of the presentinvention, the substrate on which the chips are disposed preferablycomprises a material such as ceramic. However, usable substrates alsoinclude metals, glass, plastics, and composites. It is also asignificant feature of the present invention that the polymer filmdisposed over integrated circuits as described above is removable andthereby provides a mechanism for reconfiguration and independent testingof integrated circuit chips.

It should be appreciated that the method and apparatus described abovesolves many of the significant problems associated with trying tofabricate such integrated circuits. In particular, it is seen that theapparatus and method described herein alleviate problems associated withhigh temperature processing and also problems associated with disposingfilms on irregularly shaped surfaces such as those defined by aplurality of integrated circuit chips disposed on an underlyingsubstrate. It also alleviates the problem of removing outgassingproducts.

FIG. 2A is an enlargement of a portion of the view shown in FIG. 1. Moreparticularly, FIG. 2A illustrates the conditions present before contactis made between film 35 and workpiece 33 shown herein in more detail. Inparticular, workpiece 33 includes substrate 33a on which is affixedintegrated circuit chip 37b. Also shown present on substrate 33a isundesired particle 37a, shown here only for purposes of illustration. Acoating of adhesive 36 is also shown over substrate 33a and chip 37b.Polymer film 35 is seen disposed above but not in contact with eitherthe workpiece or the adhesive. In this condition, intimate contact withthe substrate has not yet been achieved so that air and outgassingproducts are drawn out so that they do not form blisters in the finallaminated structure. This also removes undesirable contaminants from thesurface of the chip. After heating for a period of time, the adhesivemelts and pressure is applied to the top surface of film 35, asdescribed above. The resulting condition is shown schematically in FIG.2B. Note that the polymer film now complies accurately to the shape ofthe irregular substrate. Note also that the polymer film complies to theshape of particle 37a. It is important to point out here that theparticle, while undesired, is effectively covered by the polymer filmwithout the very sharp particle punching through the polymer film. Inthe case of compliant pads or rollers, a very high pressure gradientwould be produced around the area of the particle with a danger that theparticle would punch through the thin polymer film. In the presentinvention, the pressure on all areas of the polymer film is the same andcomes from a pressurized gas or liquid. This forces the best possiblecompliance to an irregularly shaped substrate, but yet prevents unduepressure gradients on edges and sharp particles. In addition, evacuatingthe area between the polymer and the workpiece ensures, intimate,void-free contact between the polymer and the to substrate.

FIGS. 3A and 3B illustrate alternate embodiments of the presentinvention and in particular, alternate combinations of polymer film andworkpiece which can be handled by the apparatus shown in FIG. 1. Inparticular, FIG. 3A shows a situation in which adhesive 36 coats anirregular workpiece. Film 50, to be bonded to the workpiece, is placedover it with second sealing film 35 actually forming the seal betweenthe vacuum and pressure areas of the structure. This configuration isadvantageous for laminating small pieces of film to a substrate. It isalso advantageous where a large continuous film might not be practical.For example, when the film to be bonded is very thin and could notsupport reliably the high pressures of the process without thepossibility of punch-through, the configuration of FIG. 3A is desirable.This configuration is also advantageous where the film to be bonded doesnot completely cover the substrate. This case occurs when a repair orinterconnect patch is being added to a substrate. FIG. 3B provides amore detailed view of the layered structures shown schematically in FIG.3A.

The adhesive shown in FIG. 2 or FIG. 3A can either be a thermoplastic, athermoset, or an ultraviolet curable adhesive Examples of curingconditions for each type adhesive are now considered. For example, whenusing a thermoplastic adhesive such as ULTEM®, the workpiece ispreferably heated to a temperature of 260° C. under vacuum for threeminutes, after which a pressure of approximately 30 pounds per squareinch is applied and cooling is started immediately. When using anacrylic adhesive, it is preferable to heat the workpiece to atemperature of approximately 200° C. under vacuum condition for threeminutes and to then apply pressure of approximately 30 pounds per squareinch, holding the temperature and pressure constant for approximately 30minutes before beginning cooling. In the case of an ultraviolet curableepoxy adhesive, the workpiece and adhesive is heated to a temperature ofapproximately 40° C. under vacuum conditions for 20 seconds after whicha pressure of approximately 30 pounds per square inch is applied. Thematerial is irradiated with 200 W/in from a Hanovia uv lamp moved slowlyback and forth across the substrate to provide uniform coverage Theepoxy is exposed for 5 to 10 seconds and the pressure is released.

An alternate embodiment of the present invention is illustrated in FIGS.3C and 3D. In this case, a thermoplastic film 51 is laminated directlyto the workpiece. Here, thermoplastic film 51 is covered by a film 35which now acts as a release film and which actually provides the sealbetween the vacuum and pressure areas. Substantial flow of thethermoplastic film can be accommodated because release film 35 complieswith the substrate, but does not flow. An example in accordance withthis embodiment employs a polysulfone film such as 1 mil thick UDEL™film made by Union Carbide. This film is heated to a temperature ofapproximately 250° C. in vacuum and a pressure of approximately 20pounds per square inch is thereafter applied following which slowcooling is initiated after about one minute at 250° C. FIG. 3D providesa more detailed view of the layered structures shown schematically inFIG. 3C.

FIGS. 3E and 3F show another embodiment of the present invention Incases where thermoplastic material 51 adheres well to the overlyingrelease film 35, metal layer 52 can be deposited on the thermoplasticbefore the laminating cycle. Here thin metal layer 52 preventsthermoplastic 51 from actually contacting overlying laminating layer 35and thereby prevents adhesion between thermoplastic 51 and overlyinglayer 35. For example, in this embodiment, a 1,000 angstrom thick layerof chromium, together with a 2,500 angstrom thick layer of aluminum maybe deposited on a polysulfone film. See FIG. 3F for a detailed view ofthe layered structure shown in FIG. 3E.

In yet another embodiment of the present invention, it is possible tolaminate a dry film photoresist using the method and apparatus of thepresent invention. For example, dry film photoresist such as RISTON™ (assupplied by Dupont de Nemours Company, Inc.) consists of three primarylayers: MYLAR™ carrier layer 54, resist layer 53 and an adhesive layer36. The material is designed to be laminated in a roll laminator.However, if an irregular substrate is encountered, the dry film resistcan be laminated as shown in FIG. 3G using the apparatus of

FIG. 1 For this film, a temperature of 100° C. for a period ofapproximately one minute, with a pressure of approximately 30 pounds persquare inch is sufficient to give very adherent, well-compliedphotoresist coverage. The carrier layer 54 can also be used as the seallayer 35 in yet another embodiment. See also FIG. 3H for a detailed viewof the layer structure.

It is also possible to employ a thermoplastic film as the film whichalso forms the seal between the vacuum and pressure regions. FIGS. 4Aand 4B illustrate two embodiments of the present invention which permitsthis kind of lamination. In FIG. 4A, metal foil 55, such as aluminum, isplaced under the workpiece and continues out to the sealing regions.Thermoplastic film 35 covers the workpiece. On subsequent heating,thermoplastic film 35 softens and adheres both to the substrate and tometal foil 55. If the foil were not placed under the substrate and outto the sealing regions, the thermoplastic material would tend to stickto the substrate holder assembly and not allow removal of the substrate.This is undesirable. FIG. 4B illustrates an alternate embodiment of thisprocedure in which metal foil 55' possesses a cutout or cutouts toaccommodate the substrate and to also thereby allow radiant energy toimpinge directly on the substrate from below and so as to thereby heatthe workpiece more efficiently.

FIG. 5 illustrates yet another embodiment of the present invention inwhich a cooled copper insert 60 is provided around the workpiece toprevent the melting of the thermoplastic layer beyond the edges of theworkpiece and to thereby prevent adhesion of the thermoplastic to thesubstrate holder assembly.

FIG. 6 illustrates yet another embodiment of the present invention andparticularly shows a side view of the basic pressure laminator of FIG. 1adapted for roll-to-roll processing. In this system, adhesive coatedworkpieces, such as 33, are fed at right angles to the direction ofmotion of polymer film 35. As each new substrate is positioned on thesubstrate holder assembly, the pressure chamber assembly is forced overthe polymer film, thereby making a seal for both the vacuum section andthe pressure section. The evacuating, pressurizing, heating, applicationof radiant energy and cooling by gas flow, as required for the process,take place as described above. When the substrate is sufficientlycooled, the pressure chamber is retracted and the polymer film is rolledfrom supply reel 65 to such a position that the laminated substratemoves from right to left with a new portion of film 35 transported intothe laminating position and a new substrate is positioned in thesubstrate holder assembly. At this point, the process can be repeated.Substrates are either rolled up on the takeup roll or punched out of thecenter of the film by punch 64. The process can also be adapted toincorporate film cleaning and inspection apparatus so that defectiveportions of the film can be bypassed simply by continuing the rollingprocess until the film overlying the substrate is free of defects.Throughout the discussion thus far, the adhesive has been described asbeing present on the substrate. It is equally possible to apply theadhesive directly to the polymer film. A suitable process in whichadhesives are applied to the film is now presented. For example, oneside of a KAPTON™ polyimide film as supplied by Dupont de NemoursCompany, Inc. is etched for 6 minutes at 300 watts in a gas comprising50% CF₄ and 50% oxygen at a pressure of 0.4 torr in a barrel plasmaetcher. A solution of 26 gram ULTEM® (as supplied by the GeneralElectric Company) resin, 104 grams of methylene chloride and 155 gramsacetophenone is sprayed on the etched KAPTON™ film. The etched andsprayed film is dried at a temperature of approximately 180° C. forthree minutes, after which it is baked at a temperature of 350° C. forapproximately five minutes.

It is noted that the apparatus and method described herein provides anextremely convenient, economical and facile mechanism for coveringintegrated circuit chips which are disposed on an underlying substrate.The presence of the circuit chips provides one of the most significantof the irregularly shaped surfaces contemplated herein. It is noted,however, that the advantages of the present invention are nonethelessobtainable even when only a single chip is covered in accordance withthe present invention. In particular, apertures are provided in thepolymer film, as by laser methods such as described in concurrentlyfiled application Ser. No. 912,455, filed Sept. 26, 1986, now U.S. Pat.No. 4,714,516, issued Dec. 22, 1987, titled "Method to Produce Via Holesin Polymer Dielectrics for Multiple Electronic Circuit Chip Packaging".This patent, assigned to the same assignee as the present invention, ishereby incorporated herein. A layer of metallization may then bedeposited and patterned so as to provide interconnections betweenvarious interconnection pads on the circuit chips. In this way,connections can be made to different parts of the same chip or betweenchips. A significant advantage of the present invention is that thepolymer film is removable. This provides a mechanism for testing andlater reconfiguration. A multichip integrated circuit packagingconfiguration and method in accordance with the present invention isdisclosed in concurrently filed application Ser. No. 912,456, filedSept. 26, 1986, now U.S. Pat. No. 4,783,695 also assigned to the sameassignee as the present invention. This patent application is alsohereby incorporated herein by reference.

From the above, it should be appreciated that the method and apparatusof the present invention provide significant advantages in the packagingof electronic circuit chip components. In particular, it is seen thatthe method and apparatus of the present invention provide a means forconstructing wafer scale integrated circuit chip devices in anindependent fashion enabling testing and reconfiguration of the devices.Most importantly, it is seen that the method of film deposition of thepresent invention alleviates problems associated with high temperaturecompliance of films to irregular surfaces. It is also seen that the filmof the present invention can be removed from the devices, such as bydisposing the resultant product in a suitable solvent such as methylenechloride. It is also seen that all of the foregoing objects are fullymet by the method and apparatus disclosed herein.

While the invention has been described in detail herein in accord withcertain preferred embodiments thereof, many modifications and changestherein may be effected by those skilled in the art. Accordingly, it isintended by the appended claims to cover all such modifications andchanges as fall within the true spirit and scope of the invention.

We claim:
 1. An apparatus for applying a polymer film to an irregularworkpiece, said apparatus comprising:a substantially flat substrateholder assembly for supporting said workpiece and said polymer film oversaid workpiece; a movable chamber sealable against a first surface ofsaid holder assembly and said polymer film; a film riser disposed onsaid first surface of said holder assembly so as to support said filmover but not in substantial contact with said workpiece; means to applyvacuum conditions to a volume bounded by said holder assembly and saidpolymer film; and means for heating said film, said means for heatingincluding an infrared transparent window in an outside wall of saidmovable chamber positioned allow heating of said film by an externalheater.
 2. An apparatus for applying a polymer film to an irregularworkpiece, said apparatus comprising:a substantially flat substrateholder assembly for supporting said workpiece and said polymer film oversaid workpiece; a movable chamber sealable against a first surface ofsaid holder assembly and said polymer film; a film riser disposed onsaid first surface of said holder assembly so as to support said filmover but not in substantially contact with said workpiece; means toapply vacuum conditions to a volume bounded by said holder assembly andsaid polymer film, said means to apply vacuum conditions including asecond chamber sealable against the second surface of said holderassembly at a point thereon opposite said film riser, the volume definedby said second chamber and said holder assembly being in flowcommunication with the volume defined at least apart by said polymerfilm and said holder assembly; and means for heating said film, saidmeans for heating said film including a heat disposed within said secondchamber.
 3. The apparatus of claim 2 in which said holder includes aninfrared transparent window on which said workpiece is disposable.
 4. Anapparatus for applying a polymer film to an irregular workpiece, saidapparatus comprising:a substantially flat substrate holder assembly forsupporting said workpiece and said polymer film over said workpiece;said holder assembly including a low thermal mass portion on which saidworkpiece is disposable; a movable chamber sealable against a firstsurface of said holder assembly and said polymer film; a film riserdisposed on said first surface of said holder assembly so as to supportsaid film over but not in substantial contact with said workpiece; meansto apply vacuum conditions to a volume bounded by said holder assemblyand said polymer film; and means to heat said film.
 5. The apparatus ofclaim 4 wherein said holder includes cooling means configured to form arecess in which said workpiece is disposable.
 6. An apparatus forapplying a polymer film to an irregular workpiece, said apparatuscomprising:a substantially flat substrate holder assembly for supportingsaid workpiece and said polymer film over said workpiece; said holderassembly including an infrared transparent window on which saidworkpiece is disposable; a movable chamber sealable against a firstsurface of said holder assembly and said polymer film; a film riserdisposed on said first surface of said holder assembly so as to supportsaid film over but not in substantial contact with said workpiece; meansto apply vacuum conditions to a volume bounded by said holder assemblyand said polymer film; and means to heat said film.